Our previous genome-wide association study identified LH/choriogonadotropin receptor (LHCGR) as a susceptibility gene for polycystic ovary syndrome (PCOS). The objective of this study was to determine whether the genetic or epigenetic components associated with LHCGR participate in the pathogenesis of PCOS. The exons and flanking regions of LHCGR were sequenced from 192 women with PCOS, and no novel somatic mutations were identified. In addition, the methylation statuses of 6 cytosine-phosphate-guanine (CpG) sites in the promoter region of LHCGR were measured by pyrosequencing using peripheral blood cells from 85 women with PCOS and 88 control women. We identified 2 hypomethylated sites, CpG -174 (corrected P = .018) and -111 (corrected P = .006). Bisulfite sequencing then was performed to replicate these findings and detect additional CpG sites in the promoter. CpG +17 was significantly hypomethylated in women with PCOS (corrected P = .02). Methylation statuses were further evaluated using granulosa cells (GCs), and the region described was hypomethylated as a whole (P = .004) with 8 significantly hypomethylated sites (CpG -174, -148, -61, -43, -8, +10, +17, and +20). Transcription of LHCGR was elevated in women with PCOS compared with that in control women (P < .01). These findings were consistent with the decreased LHCGR methylation status associated with PCOS. The tendency of LHCGR to be hypomethylated across different tissues and its corresponding expression level suggest that hypomethylation of LHCGR is a potential mechanism underlying susceptibility to PCOS. Further studies are needed to evaluate whether a causal relationship exists between LHCGR methylation status and PCOS.